OmG!
uname gave me the fact that I was running the previous kernel! I tried so many things to explain all the behaviour I was constantly seeing,
I'm not a noob anymore, but now I really dropped my trousers.

For some reason, in previous gentoo installations, I didn't have to
mount boot. It was probably done automatically, but with the new one I apparently changed this (which is a good thing I believe). So here I was
compiling new kernels, copying them to /boot, checking to see if they were copied, updating my linux link... and probably was doing all
that virtually!? Mounting the boot did the trick, after that my modules loaded, eth0 was working again and even the ati-drivers with
fglrx!! Incredible, weeks I spend behind the screen for this.
So, what works for me on this system is gentoo 2.6.16-r6 with ati-drivers 8.23.7, not forgetting to mount /boot when copying new kernels:
- Ati Radeon 9600
- SiS chipset controllers
- Realtek, SiS ethernet controllers
Thanks m8's!